It is essential to hermetically seal semiconductor dies from the surrounding atmosphere so that they are impervious to water vapor and other moisture in the air. If the metallization on the semiconductor die active surface is allowed to contact water vapor or other moisture, or other atmospheric gases, the operation of the active circuitry can be effected, the life of the IC circuit can be effected, etc. To prevent the contact of moisture and gases with the metallization on the semiconductor die, it is common to encapsulate the die so as to hermetically seal it from the atmosphere.
In most prior art devices, semiconductor dies are hermetically sealed by using ceramic or metal enclosures which are relatively expensive and complicated to manufacture. Also, substantial labor is required in mounting the die within the ceramic or metal enclosure and connecting external leads thereto. In one prior art device disclosed in U.S. Pat. No. 3,325,586, entitled "Circuit Element Totally Encapsulated in Glass", issued June 13, 1967, semiconductor dies are sandwiched between two flat plates, which may be constructed of metal or ceramic, with an unfired glass material and the entire sandwich is fired to completely encapsulate the die between the two plates. While this apparatus is somewhat of an improvement over the prior packages, it still requires considerable labor and effort in positioning the plates and placing the unfired glass material around the die therebetween.